Yttria nanopowders with low degree of aggregation by a spray precipitation method

Highly sinterable Y₂O₃ nano-powder with low degree of agglomeration was synthesized by using a spray precipitation technology, without the use of any additives and dispersants. Compared with the precursor made by using the dripping method (D-precursor), the precursor made by the spraying method (S-precursor) had much lower degree of hard agglomeration. So did the resultant calcined Y₂O₃ powder (S-Y₂O₃ powder) as compared with the D-Y₂O₃ powder. Sintering behaviors of the two powders were studied. Ceramics made from the S-Y₂O₃ powder (S-Y₂O₃ ceramics) showed much higher densification rate and final density. After vacuum sintered at 1650 °C for 5 h, relative density of the D-Y₂O₃ ceramics was merely 97.3%, while that of the S-Y₂O₃ ceramics reached 99.5%. In addition, the D-Y₂O₃ ceramics cannot be sintered to 98% relative density by using the vacuum sintering technique, due to the high degree of agglomeration of the D-Y₂O₃ powder. Moreover, the S-Y₂O₃ ceramic exhibited homogeneous microstructure and an in-line optical transmittance of 81.6% at 1200 nm after HIP treatment. The spray precipitation method should be applicable to synthesizing other oxide powders.